Human Embryo Fibroblasts (HEF) will be grown in culture flasks with various radiolabeled precursors of membrane phospholipid. Once the cells have incorporated the precursors and reached a stationary phase the medium will be washed out and fresh medium which contains the same precursor with a different isotope will be added. Some of the cell cultures will be infected with Herpes Simplex Virus - Type II, others are mock-infected to serve as controls. Samples taken at various incubation times will be extracted with organic solvent and the lipids counted and separated by thin-layer chromatography. Any variation in membrane phospholipid turnover can be detected in this manner, including both synthesis and degradation. Once these general metabolic alterations are established, we can investigate two major areas; one, the changes that occur under growth conditions which lead to productive infection, abortive infection, or transformation, and two, the origin of the lipid envelope of the virus. The origin of the lipid will be determined by isolation of the virus and comparison of the envelope phospholipid with that of the cellular membranes which are isolated by differential and gradient centrifugation. The comparisons to be made are both quantitative (radiolabel and lipid phosphorus content) and qualitative. Special attention will be paid to the nuclear membranes which are thought to be the direct source of the virus lipid component and the endoplasmic reticulum which is the site of phospholipid synthesis de novo. Comparison of the isotope ratio should indicate how much of the preexisting nuclear membrane was incorporated into the virus envelopes and how much was derived from membrane transferred from the endoplasmic reticulum in response to viral replication.